1. Field of the Invention
The present invention relates to a sealing member for use in a process cartridge detachable from an electrophotographic image forming apparatus for forming an image on a recording medium. The present invention also relates to a process cartridge using the sealing member.
A typical process cartridge is a cartridge in which an electrophotographic photosensitive drum and at least one of a charging unit, a developing unit, and a cleaning unit are integrally formed, and it is detachable from a main body of an image forming apparatus. In the present invention, a developer containing portion is a necessary element. Therefore, a process cartridge that includes a developer containing portion is discussed.
An electrophotographic image forming apparatus is one that forms an image on a recording medium using the electrophotographic image forming technique. Examples of the electrophotographic image forming apparatus include, but not limited to, an electrophotographic copier, an electrophotographic printer (e.g., a laser beam printer, a light-emitting diode (LED) printer), and a facsimile machine.
2. Description of the Related Art
Traditionally, an electrophotographic image forming apparatus employs a system of enabling a process cartridge in which an electrophotographic photosensitive member and a process unit that acts on the electrophotographic photosensitive member are unitized to be detachable from the main body of the image forming apparatus.
In such a process cartridge, in order to prevent leakage of a developer from a developer containing portion to the outside, a plurality of sealing members are disposed between frames constituting a process cartridge and parts. For example, in order to prevent leakage of a developer to the outside of a development frame in a process cartridge, a sealing member is disposed between a developer regulation member and the development frame.
One known example of a material of a sealing member is an elastic body, such as a urethane foam. A method of making the sealing member being deformed by a predetermined depression quantity come into contact with a sealing portion to seal against leakage of a developer is generally employed (see, for example, Japanese Patent Laid-Open No. 11-272071).
A urethane foam as a sealing member is typically attached on a development frame using double-sided adhesive tape provided on a substrate. When a developer regulation member is imposed in a state where the urethane foam is attached, the urethane foam being deformed by a predetermined depression quantity is thus inserted between the development frame and the developer regulation member. Accurately attaching the urethane foam using double-side adhesive tape requires much effort. Additionally, release paper from the double-sided tape is present as discarded material, so the amount of the discarded material increases with an increase in production.
To address this issue, the use of a thermoplastic elastomer in place of a urethane foam is being examined, and in particular, directly molding the thermoplastic elastomer into a sealing member on a development frame is being examined. If the thermoplastic elastomer is used, in order to prevent adverse effects of deformation of the development frame and the developer regulation member on the image quality, it is useful that resilience of the thermoplastic elastomer be minimized. However, if the molecular weight is too lowered in order to reduce the hardness of the thermoplastic elastomer, a plasticizer contained in the thermoplastic elastomer may seep after it is left under high temperature conditions for a long period of time, toner particles may be fused together, and thus an image defect, such as a vertical line, may tend to occur in an image. Accordingly, it is desired that fusing toner particles together be reduced and the occurrence of an image defect, such as a vertical line, in an image be reduced.